Production of fluids from unconsolidated formations



April 5, 1966 K. HuJsAK ETAL PRODUCTION OF FLUIDS FROM UNCONSOLIDATED FORMATIONS 2 Sheets-Sheet 1 Filed April 12, 1963 M E E M M E M w -30 40 MESH HOURS KAROL HUJSAK W|LL|AM G. BEARDEN INVE N TORS B y 74 C% ATTORNEY.

April 1966 K. L. HUJSAK ETAI. 3,244,229

PRODUCTION OF FLUIDS FROM UNCONSOLIDATED FORMATIONS Filed April 12, 1963 2 Sheets-Sheet 2 EA y/ Y0K KAROL L. HUJSAK WILLIAM G. BEARDEN INVENTORS.

ATTORNEY.

United States Patent 3,244,229 PRODUCTION OF FLUIDS FRGM UNCON- SOLIDATED FORMATIONS Karol L. Hujsak and William G. Bearden, Tulsa, Okla,

assignors to Pan American Petroleum Corporation,

Tulsa, Okla, a corporation of Delaware Filed Apr. 12, 1963, Ser. No. 272,723 17 Claims. (Cl. 166-12) The present invention relates to the production of fluids from loosely consolidated sands. More particularly, it is concerned with a novel improvement in the problem of controlling the flow of sand in hydrocarbon fluids produced either by means of conventional oil wells or by means of wells that are part of an underground combustion project.

Briefly stated, our invention involves the useof a particulate solid material which, when contacted with a liquid, tends to adhere to adjacent particles of said material to form a rigid or fixed filter pack suitable for preventing the flow of sand into the well producing system. Sand control in wells producing from unconsolidated formations is a major problem. This is true not only in conventional oil wells producing from unconsolidated zones, such as are found in the gulf coast area, but also -the matter of sand control remains a serious problem in the recovery of oil from tar sands by thermal methods where high temperatures are encountered in addition to loosely cemented formations.

When a well penetrating an unconsolidated oil producing, sand is placed on production, sand erodes from the formation and deposits in thewell. The presence of such sand in the well gives rise to a number of operating problems. In fact, they can be sufficiently serious to require abandonment of the well. In other instances this loose sand requires frequent workover jobs in order for the well to operate efliciently. In addition, removal of sand which accumulates in surface equipment such as flow lines, tanks, or separators adds substantially to the cost of production.

Sand filters such as slotted liners or screens have. been i proposed for the purpose of combatting this problem.

Such equipment is usually inserted within the production tubing and placed opposite the producing formation. Packers are used as required to isolate the producing formation and then oil can flow directly from the formation through the liner or screen into the tubing. In spite of theseliners or screens, however, sand production still occurs and frequent workover jobs are necessary to maintain satisfactory production.

Gravel packing is still another technique that has been employed in an attempt to solve the sand production problem. In such cases a coarse sand (referred to as gravel) is packed around a wire-wrapped or slotted screen liner. This technique, however, fails to completely prevent sand production and plugging of Wells employing this procedure frequently occurs. Such packing appears to be defective, at least in part, for the reason that the gravel tends to shift or move even when packed in place. Movement of the gravel, in turn, causes the sand back of it to move, Working its way through the gravel pack, abrading the liner, and allowing both gravel and sand to enter the well.

In the case of recovering oil from tar sands by means of combustion, we not only have the above-mentioned sand control problems but are, in addition, confronted with the difficulty of providing materials of construction capable of withstanding temperatures of the order of 1500 to 2000 F.

In the drawings, FIGURE 1 is a series of curves demonstrating the relationship of time and cement clinker 3,244,229 Patented Apr. 5, 1966 particle size to permeability of a well liner constructed of cements contemplated by the present invention;

FIGURE 2 is a sectional elevational view of a well producing from two separate zones in which the cement clinker composition of the present invention is deposited behind the casing and opposite the producing zones to restrain sand fiow into the well;

FIGURE 3 is, likewise, a sectional elevational view showing another variation of the manner in which the ground cement clinker compositions of the present invention can be employed to restrain the flow of sand from incompetent formations while at the same time permittin g the flow of liquids therefrom.

It is, accordingly, an object of our invention to provide a dependable means of controlling sand flow both in ordinary producing oil wells and in wells producing liquid hydrocarbons from tar sand or similar deposits by combustion methods. It is also an object of our invention to provide a means of placing a porous or permeable pack of material opposite a producing zone in a well wherein the components of the pack are more or less locked in position and will not shift when formation fluids flow through them and into the well. It is a further object of our invention to provide a method for completing a Well penetrating a number of incompetent or unconsolidated producing zones. It is still a further object of our invention to provide a means by which a single, relatively thick, unconsolidated producing formation can be treated so as to produce hydrocarbon fluids therefrom without the accompanying entrainment of sand. It is another object of our invention to provide a preformed permeable well line to serve as a means of sand control in either conventional producing or combustion wells.

In carrying out an embodiment of our invention, we use a ground hydraulic cement clinker prepared from calcium silicate, high alumina cement, or calcium aluminate. The ground material may be placed in position in essentially the same manner as a gravel pack, i.e., introduced in dry form. However, the pack resulting from the use of cement clinker differs markedly from that made of gravel since the particles of clinker in the presence of Water, which is ordinarily standing in the well, hydrate and bond to one another at points of contact. In this way, a rigid filter is formed which prevents sand from entering the well while at the same time permitting fluids to be produced in normal fashion. The high strength of the resulting filter pack is beneficial for the reason that it lends support to the incompetent formation and thereby prevents movement of the sand grains therein.

As a source of suitable ground material we have found highalumina cement clinker to be particularly effective. The clinker may be converted for use in our invention in a number of different ways. For example, it can be passed through a coarse grinder, then screened to pro vide the desired particle size distribution. In this regard, tests have shown that high alumina cement (Lumnitea calcium aluminate cement) clinker ground to .a particle size ranging from about -10 to about +40 mesh, when allowed to set properly, can have a tensile strength in excess of 200 p.s.i., a compressive strength of 1.500 p.s.i., and a permeability as high as 60 darcys. The effect of time and particle size on the ground clinker, as used in our invention, on permeability is shown in the plots appearing in FIGURE 1. Thus, it is seen that with the coarser particle size, within the broadly stated range given above, the permeability is the highest. In the case of the -12 to +20 mesh material, it will be observed that a permeability of about 60 darcys was maintained, even after about 33 days, whereas with a pack prepared from 30 to +40 mesh high alumina cement clinker the permeability for the same length of time was 8.5 darcys.

While this represents a substantial decrease, of course, in permeability, it will be recognized as ample for securing sustained production.

One interesting fact in this connection, however, is that Portland cement clinker ground to a particle size ranging from -l() to +40 mesh fails to develop adequate strength in a reasonable length of time, e.-g., about days. Thus, with two batches of standard Portland cement clinker (ASTM Type 1), one sample ranging in particle size from 14' to +30 and the other from 3() to +100 failed to develop a tensile strength of over 1 p.s.i. when allowed to set for 112 hours at 70 P. On the other hand, separate batches of Lumnite cement clinker having the same particle size ranges developed 222 p.s.i. tensile strength for the coarser grind, i.e., -14 to +30, and a tensile strength of 483 p.s.i. for the -30 to +100 material. The permeability of the coarser ground Lumnite clinker was 13 darcys, while the smaller particle size material was found to have a permeability of about 1'2 millidarcys.

Our invention may be further illustrated by reference to FIGURES 2 and 3, showing different applications of the high alumina clinker composition in unconsolidated or incompetent formations. In FIGURE 2, a well 2 penetrates two unconsolidated oil producing formations 4 and 6 separated by an impervious zone 8. Casing 10 extends from the surface down to a level a short distance below unconsolidated zone 6. When casing has been set to the level just mentioned, a suitable bridging plug 12 is placed about even with the lower end of casing 10. However, if casing is run essentially the entire length of the Well, no plug need be used. Thereafter, perforations 14 are made and the well placed in communication with formation 6. A batch of high alumina cement clinker" is next displaced down the well and into formation 6 via perforations 14 to contact the incompetent format-ionover an area comparable to the crosshatched portion shown as 16. Usually, excess cement remaining in the well after an operation of this sort can be immediately washed out.

Similarly, opposite formation 4 perforations 18 are made in the casing and temporary bridging plug (not shown) set opposite zone 8. If formations 4 and 6 are close enough, the cement clinker, in slurry form, may be squeezed intosaid formations in a single operation and the excess material washed or later drilled out before completion.

With the cross-hatched portion 20 now filled with a permeable high alumina cement clinker, tubing 22 holding packers 24 and 26- is run into the well and the packers set. After packer 26, which is a dual string production packer, has been set, production tubing 28 is run and extends into the zone defined by the packers 24 and 26. In case formation 4 is in a reservoir having adequate energy, packer 26 need not be used, the oil being produced up the annulus.

In the embodiment as shown in FIGURE 2, the loose sand in formations 4 and 6 is restrained or controlled by the deposits of high alumina cement clinker; and oil, free from objectionable amounts of solids, is produced up the well via tubing strings 28 and 22, respectively, after which it is removed via separate flow lines 30 and 32. The set cement clinker, shown as 16 and 20, may be placed in the well either in the form of dry ground clinker or as an aqueous slurry. Usually, there is enough water present in the well to hydrate the cement if it is placed at the desired level in dry form.

FIGURE 3 shows a well 34. completed in a relatively thick section of unconsolidated oil producing sand in which casing 36 is run into the pay and a plug 38 is set just below-the portion of the zone to be produced. Next, perforations 40 are made in the casing over a distance of, for example, 10' to 20 feet, after which a suflicient quantity of a pumpable mixture of high alumina cement clinker is displaced down the well to form. a column extending approximately from the lowermost of perforations 40 to about the upper portion of sand 35, or at least above the upper line of perforations. While cement is still soft, a drillable sub 42, e.g., made of a soft metal or plastic, having slots 44 is run in on tubing string 46. Alternatively, the cement may be added after sub 42 is in place. The plastic pipe 42 is held in proper alignment with the well by means of centralizers 48. Once cement column 41 has set, oil from sand 35 flows into the well via perforations 40 through the permeable cement and into plastic sub 42. There is no movement of sand toward the well beyond perforations 40.

If, for any reason, it is desired to produce from a level below that shown in FIGURE 3, tubing 46 may be separated from sub 4-2 by means of a back-off or tool joint 50, the tubing pulled and the cemented section, including plastic sub 42 and bridging plug 38, drilled out.

Alternative to the embodiments just discussed, the cement clinker could be placed behind casing in the usual fashion opposite perforations at the level of the producing zone. In such case, the slurry of clinker is preferably suspended in an aqueous gel such as can be formed from gnar, batu, locust bean gums, and the like. In this way, the particles do not settle out and block the space behind the casing before it is adequately packed with clinker. When the slurry thus placed is permitted to set properly, oil can flow into the Well from the unconsolidated formation without any concern about being hampered by entrained sand.

Also, instead of using the cement pack of our invention as a filter surrounding a perforated sub section attached to the production string, we may deposit a slug of such cement in the well opposite the unconsolidated zone as an oil-permeable plug. In this way the oil can be allowed to flow from said zone, percolated through such plug and removed via tubing which extends to a level just a short distance above said plug. Or, when it is desired to consolidate the incompetent portion of an open hole oil-producing zone, a plug prepared from the cements. taught herein can be placed opposite said zone and after such plug has set properly, a hole of smaller diameter is drilled into the plug leaving a lining of permeable cement adjacent the formation, thus permitting sand free oil to flow through the plug and into the well bore.

While the composition of the high alumina cement may vary to some extent, it should generally contain (on a dry basis) 35v to 45 percent A1 0 30 to 40 percent CaO, up to 15 percent Fe O and a combined percentage of silicon and magnesium oxides of from 5 to 10 percent. The expression, high alumina cement, therefore, as used in the present claims is to be construed as referring to cement mixes of the composition noted immediately above. The preformed well liner previously mentioned may be prepared by any of several different procedures.

For example, a suitable cylindrical form having an annulus, typically one to three inches in width, is placed in a vertical position and an aqueous slurry of the ground cement clinker poured into the annular space. Such a form is conveniently made of concentric rolls of thin sheet metal equal in length. The outer roll may be held in place by means of metal straps or the equivalent while the inner member is held in shape by means of metal clamps or internal cross bracing When the cement has 'had time to set properly, the metal straps and bracing are removed and the inner and outer metal rolls separated from the newly formed liner. If desired, these liners may be reinforced on either the outside or inside, or both, by placing hardwear cloth, expanded metal screen, etc. on theinside wall of the outer roll and on the outside wall of the inner roll.

In installing these. liners, they may be run into the Well on tubing and placed opposite the incompetent oil producing zone. Methods for running screens of this kind intoa. well have been practiced for many years.

Typical of such procedures are those described in expired US. Patents Nos. 2,154,461 and 2,167,190 as well as 2,205,422.

In placing the oil permeable packs of our invention, we have found that the presence of sodium chloride in excess of about 5 grams/100 ml. of water interferes with the development of the proper strength of the cements contemplated herein. Thus, while particles of a high alumina cement clinker hydrating in the presence of tap water and in' a 5 weight percent sodium chloride solution developed compressive strengths of 1318 psi. and 141 p.s.i., respectively, in 72 hours, such cement in contact with a solution of grams of sodium chloride in 100 ml. of waterv had no compressive strength after the same period. This adverse effect of sodium chloride brines, however, can be counteracted by the addition of calcium chloride, usually in a concentration at least equal to that of the sodium chloride.

We claim:

1. A method of forming a fixed filter pack adjacent an incompetent oil-producing zone penetrated by a well,

comprising placing a ground hydraulic cement clinker selected from the group consisting of calciumsilicate, calcium aluminate, and high alumina cements in contact with the portion of said zone exposed to said Well, said clinker having a particle size ranging from about -10 to about mesh, allowing the particles of said clinker to bond together by means of hydration at the points of contact to form a rigid oil-permeable pack, and producing oil from said zone through said pack into said well substantially free from abrasive solids.

2. A method of forming a fixed filter pack adjacent an incompetent oil-producing zone penetrated by a Well, comprising placing high alumina cement clinker in contact with the portion of said zone exposed to said well, said clinker having a particle size ranging from about 10 to about +40 mesh, allowing the particles of said clinker to bond together by means of hydration at the points of contact to form a rigid oil-permeable pack, and producing oil from said zone through said pack into said well substantially free from abrasive solids.

3. The method of claim 1 in which calcium aluminate cement clinker is employed.

4. A method of forming a fixed filter pack adjacent an incompetent oil-producing zone penetrated by a well, comprising placing an aqueous slurry of high alumina cement clinker in contact with the portion of said zone exposed to said well, said clinker having a particle size ranging from about 10' to about +40 mesh, allowing the particles of said clinker to bond together by means of hydration at the points of contact to form a rigid oilpermeable pack between said zone and said well, and producing oil from said zone through said pack into said well substantially free from abrasive solids.

5. A method of forming a fixed filter pack adjacent an incompetent hydrocarbon-producing zone penetrated by a well having a string of production tubing carrying a perforated subsection at the lower end thereof, comprising placing said subsection opposite at least a portion of said zone so that said subsection and said zone are in direct communication with one another, thereafter displacing high alumina cement clinker into the annular space between said zone and said subsection, said clinker having a particle size ranging from about 10 to about +40 mesh, next allowing said cement clinker to set whereby a rigid filter pack is formed about said subsec tion, and producing hydrocarbons from said zone through said pack into said well substantially free from abrasive solids.

6. The method of claim 2 in which the particle size of the high alumina cement clinker ranges from about --10 to about +30 mesh.

7. A method of preventing the influx of loose sand or abrasive particles into a cased well penetrating an incompetent hydrocarbon-producing zone, said well having' a string of production tubin'g therein and carrying a perforated subsection on the lower end of said string, said casing having perforations opposite said zone, comprising placing said subsection at a level in said well in proximity to said perforations, displacing a sufficient quantity of high alumina cement clinker down said casing to cover said perforations, said clinker having a particle size ranging from about 10 to about +40 mesh, allowing said clinker to set to form a rigid, permeable pack about said subsection, and producing hydrocarbons fromv said zone through said pack and into said well.

8. A method of forming a fixed filter pack adjacent an incompetent hydrocarbon-producing zone penetrated by a cased well, said casing having perforations opposite said zone, comprising forcing a slurry of high alumina cement clinker into said zone and behind said casing via said perforations, said clinker having a particle size ranging from about l0 to about +40 mesh, allowing said particles of clinker to hydrate and set, and thereafter producing hydrocarbons substantially free from sand from said zone through the resulting mass of said cement and into' said well via said perforations.

9. A method of forming a separate fixed filter pack in each of two spaced incompetent hydrocarbon-producing zones penetrated by a cased well, said casing having perforations opposite each of said zones, comprising selectively displacing a slurry of a ground hydraulic cement clinker selected from the group consisting of calcium silicate, calcium aluminate and high alumina cements into one of said zones and behind said casing via the perforations opposite said one of said zones, said cement clinker having a particle size ranging from about 10 to about +40 mesh, next selectively displacing an additional quantity of said slurry into the other of said zones via the perforations opposite said other of said zones, allowing said particles of clinker thus deposited in both of said zones to set, and thereafter producing hydrocarbons substantially free fromsand from both of said zones through each of the set deposits of said clinker and into said well.

10. The method of claim 9 in which the cement clinker employed is derived from high alumina cement.

11. A method of placing a deposit of cement clinker opposite an incompetent hydrocarbon producing zone penetrated by a well which comprises first forming a cavity about the well bore opposite said zone, next displacing a quantity of ground cement clinker selected from the group consisting of calcium silicate, calcium aluminate, and high alumina cements in an amount sufficient to fill said cavity and said well bore surrounded by said cavity, said clinker having a particle size range from about ---10 to about +40 mesh, allowing the particles of said clinker to bond together by means of hydration at the points of contact to form a rigid oil-permeable pack in said cavity, drilling through said pack, and thereafter producing hydrocarbons from said zone through said pack and into said Well substantially free from abrasive solids.

12. As a new article of manufacture a hollow, cylindrical, oil permeable sleeve fabricated from a ground hydraulic cement clinker selected from the group consisting of calcium silicate, calcium aluminate, and high alumina cements, said clinker having a particle size ranging from about l() to about +40 mesh.

13. The article of manufacture of claim 12 in which the cement clinker is derived from a high alumina cement having an average particle size ranging from about 10 to about +30 mesh.

14. The method of claim 11 in which calcium aluminate cement clinker is employed.

15. The method of claim 11 in which high alumina cement clinker is employed.

16. In the production of hydrocarbons by means of underground combustion from an incompetent oil-producing zone penetrated by an injection and a producing well and wherein said zone is ignited and an oxygen-contain- :ing gas is introduced into said zone via said injection Well whereby said hydrocarbons are forced into: said producing well, the improvement which comprises, prior to said ignition step, placing a ground hydraulic cement clinker selected from the group consisting of calcium silicate, calcium aluminate, and high alumina cements in contact with the portion of said zone exposed to said well, said clinker having a particle size ranging from about 10 to +40 mesh, allowing the particles of said clinker to bond together by means of hydration at the points of contact to form a rigid oil-permeable pack, and producing oil from said zone through said pack into said well substantially free from abrasive solids.

17. The method of claim 16 in which high alumina cement clinker is employed.

References Cited by the Examiner UNITED STATES PATENTS Paulsen 166228 Woods 166-12- Coberly 166--228 Williams 166-228 Arendt et .al.v 166-47 Mangold et a1. 16612 Killingsworth 166-228 Johnson 16642.1 Ladd et al. 166-12 Dixon 166-15' CHARLES OCONNELL, Primary Examiner. 15 T. A. ZALENSKI, Assistant Examiner. 

1. A METHOD OF FORMING A FIXED FILTER PACK ADJACENT AN INCOMPETENT OIL-PRODUCING ZONE PENETRATED BY A WELL, COMPRISING PLACING A GROUND HYDRAULIC CEMENT CLINKER SELECTED FROM A GROUP CONSISTING OF CALCIUM SILICATE, CALCIUM ALUMINATE, ANDHIGH ALUMINA CEMENTS IN CONTACT WITH THE PORTION OF SAID ZONE EXPOSED TO SAID WELL, SAID CLINKER HAVING A PARTICLE SIZE RANGING FROM ABOUT -10 TO ABOUT +40 MESH, ALLOWING THE PARTICLES OF SAID CLINKER TO BOND TOGETHER BY MEANS OF HYDRATION AT THE POINTS OF CONTACT TO FORM A RIGID OIL-PERMEABLE PACK, AND PRODUCING OIL FROM SAID ZONE THROUGH SAID PACK INTO SAID WELL SUBSTANTIALLY FREE FROM ABRASIVE SOLIDS. 